1. Field of the Invention
The present invention relates to a toner sorting device for separating reusable toner from used toner collected by an image forming apparatus employing electrophotography, such as copiers, facsimiles, printers, etc., and more particularly relates to a toner sorting device which efficiently separates reusable toner from used toner for recycling the reusable toner. The present invention also relates to an image forming apparatus that uses such a toner sorting device.
2. Discussion of the Background
When an image forming apparatus employing electrophotography forms an image, the apparatus first forms an electrostatic latent image of an original document on an image carrier, such as a photoconductor, which is uniformly charged, through exposure of the original or optical writing of information of the original. The latent image is then developed by a developing unit to a visible toner image with developer, such as two-component developer including toner and carrier or single component developer in which toner and carrier are integrated. The toner image is then transferred to a recording sheet by a transfer device, such as a transfer roller or belt, to form a duplicate of the original on the recording sheet. The toner image may alternatively be transferred to an intermediate transfer member, such as an intermediate transfer belt, for superimposing another toner image thereupon to form, for example, a full-color toner image, which is subsequently transferred to a recording sheet. The recording sheet carrying the toner image is then conveyed to a fixing unit by a conveying device, such as a conveying belt. The toner image is then fixed to the recording sheet by the fixing device.
The image forming apparatus further includes cleaning devices for removing residual used toner remaining on the photoconductor or the intermediate transfer member for preventing contamination of subsequent images to be formed thereupon. The image forming apparatus also includes cleaning devices for removing used toner remaining on the transfer belt and the conveying belt. The used toner collected by these cleaning devices is typically conveyed to and moved into a discardable toner bottle, i.e. a toner bottle for storing discardable toner, and is disposed of by a service person or a user of the apparatus.
Recently, demands for recycling such residual used toner collected by cleaning devices of an image forming apparatus have increased. Mechanisms for conveying collected used toner to a developing unit of the apparatus or to a toner supplying unit which supplies toner to the developing unit have been proposed.
Residual used toner collected by cleaning devices of an image forming apparatus typically includes paper dust produced from a recording sheet. Paper dust is produced, for example, when the recording sheet passes between the transfer device and the photoconductor or the intermediate transfer member. The residual used toner may also include coagulated toner particles which are larger than unused toner particles. If the residual toner is recycled for image formation, paper dust and/or coagulated toner particles included therein may cause abnormal toner images. For example, white spots may be formed in a part of an image formed by toner which includes paper dust. A part of an image formed by toner which includes a large coagulated toner particle may blur.
Therefore, some image forming apparatuses use a net member for separating alien material such as paper dust and/or coagulated toner particles from collected residual used toner to recycle only reusable toner. Because meshes of the net member tend to become clogged by toner and/or paper dust, the net member is typically vibrated to prevent clogging of the meshes of the net member by the paper dust and/or toner.
However, even when the net member is vibrated, meshes of the net member tend to become clogged if a large volume of toner is deposited on the net member. This decreases efficiency of separating reusable toner from the used toner, resulting in reusable toner not being separated from the used toner, with the reusable toner being unnecessarily discarded.
Further, large coagulated toner particles not passing through meshes of the net member may be separated from reusable toner as non-reusable toner and may be unnecessarily discarded even though the toner itself would be reusable if the coagulation were loosened.